In recent years, prisms are widely used as essential parts of various kinds of optical equipment, such as DSCs (digital still cameras), DVCs (digital video cameras), cameras for mobile phones, projection televisions, and the like, and the range of uses thereof is expanding. While, demands for higher precision, compaction, and weight reduction of the various optical equipment are increasing. In association therewith, the prisms used in the various optical equipment are required to have higher performance, such as higher precision, higher functionality, higher strength, and the like and are also required to be mounted at appropriate positions of the optical equipment.
A general triangular prism includes three side faces as optical function planes and two end faces as non-optical function planes. As a glass-made prism manufacturing method, a generally-called press molding method is known in which a material to be molded is heated and pressed and then is cooled (see, for example, Patent Document 1).
When a prism is molded by the press molding method disclosed in Patent Document 1, each ridge where the planes are intersected with one another is formed sharply. Accordingly, in handling the prism, specifically, in conveyance, in mounting to optical equipment, and the like, the ridges may be broken or chipped by external impact. For this reason, desired prism performance cannot be obtained, and the yield of the optical equipment lowers.
For tackling the above problems, namely, for suppressing breakage and chipping of the ridges, a prism of which ridges are chamfered after press molding has been proposed (see, for example, Patent Document 2).    Patent Document 1: Japanese Patent Application Laid Open Publication No. 7-69651A    Patent Document 2: Japanese Patent Application Laid Open Publication No. 61-103101A